Twilight at Waterfowl Lakes, Banff, Alberta, Sept 4, 2011, looking toward the sunset point on a very clear night with prominent twilight purple in the sky. The prominent peak in Mt. Cephren. This is a 7-image High Dynamic Range stack of exposures taken at 2/3rd f-stop intervals, using the Canon 7D at ISO 100 and 10-22mm lens at 14mm and f/5.6. (Photo by: Alan Dyer /VW PICS/UIG)